ABSTRACT In the past decade, several groups, including our own, have shown the importance of immune cell subsets on atherogenesis in mice, but we are just beginning to discover how immune cells are metabolically and transcriptionally changed during atherogenesis in humans. This PPG will focus on human cardiovascular disease, and will test the hypothesis that lipoproteins with their lipid and protein components trigger innate and adaptive immune responses that impact atherosclerosis. We will study functional changes in immune cells and the immune cell cross-talk that occurs during atherosclerosis progression in humans using the well- characterized NHLBI-sponsored longitudinal clinical cohort, Multi-Ethnic Study of Atherosclerosis (MESA), and our UVA Cardiovascular Cohort. We will study subjects who have low versus high cardiovascular risk based on their coronary artery calcium (CAC) Agatston scores. CAC Agatston scores have high positive predictive values for cardiovascular disease (CAD) events, and Agatston scores (above 300) are strong predictors of future CAD events. We will study subjects with CAC Agatston scores >300 as high risk, and we have carefully matched controls by age and gender with Agatston scores of zero as low risk. In this synergistic program, Project 1 Monocyte Subsets & Immunity in Mouse and Human Atherosclerosis, will study how monocyte subsets respond to oxidized LDL to impact cardiovascular disease. Project 2 Cholesterol Regulation of Inflammatory Macrophages in Atherosclerosis, will investigate how cholesterol modulates macrophage polarization in atherosclerosis. Project 3 B Cell Subsets in Mouse and Human Atherosclerosis, will study how specific chemokine receptors promote B cell subset migration and atheroprotection. Project 4 ApoB-Specific CD4 T cells in Mouse and Human Atherosclerosis, will test the hypothesis that apoB-specific CD4 T cells are atheroprotective by producing IL-10, but fail later in disease. An important synergistic aspect to our PPG is that B cells, T cells, monocytes and macrophages communicate with each other in the artery wall and lymphoid tissues, and each project studies one of these immune cell subsets, so there are many project interactions. Unique aspects of our program are the strong focus on studying human immune cells, the use of CyTOF mass cytometry and RNA-Seq as innovative methodologies used to study these cells, the measurement of plasma immunoglobulins using ELISA-based assays developed in our group and currently used in multiple clinical trials, and our ability to link all of our group's discoveries with a 15-year extensive MESA clinical database to understand how immune cells change to contribute to CAC progression and cardiovascular disease. The end goal of our studies is to identify novel therapeutic strategies targeting immune cell function to limit cardiovascular disease.